The present invention relates to the display of color characteristics of a television signal, and more particularly to a rectangular gamut display for determining composite legality or RGB (Red,Blue,Green) gamut violations.
Existing waveform displays plot a composite video baseband signal (NTSC, PAL, SECAM, etc.), video component signals (YUV, Y,Cr,Cb, RGB, Y,R-Y,B-Y, etc.) or a pseudo-composite signal created from the components on a y-axis against Time on an x-axis. Many users watch the waveform display for trace points that exceed their allowed y-axis values as a way of checking Composite legality or RGB gamut violations. The user is able to determine which component is in violation and at which location on the video picture, but doesn't receive information about hue, saturation or other parameters that may be useful for understanding and correcting the violations. U.S. Pat. No. 4,707,727 discloses an apparatus for providing an indication on a waveform or display monitor when a color represented by a Y, R-Y, B-Y television signal is validly reproducible on an RGB display device.
Existing gamut and legality displays, such as the Arrowhead legality display (U.S. Pat. No. 5,519,440), the Diamond gamut display (U.S. Pat. No. 5,309,087), the Spearhead gamut display (U.S. Patent Application Publication No. 2004/0218044) and the polar gamut and legality display (U.S. Patent Application Publication No. 2002/0063801), plot composite or component values against each other or against Hue in non-rectangular graphical displays in order to provide better information for understanding and correcting violations. While these graphical displays are quite elegant and do provide good information, their non-standard graph layouts are confusing to many users. The fact that there are many graph styles means that users must memorize which is useful for what (‘Diamond is for Component; Arrowhead is for Composite”; etc.) and how each one must be interpreted.
What is desired is a standard graphical layout for a gamut display that is easier for a user to use.